Matthew Williamson: 'I'm such a cliché'

As I walk up a street of grand wedding-cake villas not far from Primrose Hill in north London, it is not hard to spot where Matthew Williamson lives. Aside from a few houses painted in peeling pastels that are a throwback to the area's more bohemian past, the style is uniformly bankers-who-brunch. Lots of immaculate black ironwork and bay trees standing in sentry pairs. It is late morning, a precious day of September sunshine, but all is glossy and frozen, as if liberally sprayed with Elnett. And then I hear music drifting from one of the huge open bay windows. A string of Indian silk stuffed birds, trinket of a million 1990s gap years, spins gently in the breeze, and beyond I can see a white marble Eero Saarinen table crammed with peace lilies and an enormous Murano glass ashtray. On the white walls are a Cameroonian juju headdress in Tango orange and a Jimi Hendrix poster in vintage psychedelic font. The mantelpiece is crammed with bell jars, Mexican votive candles and vintage frames of pinned butterflies.

The man who invented boho-glamour, who convinced perfectly sane British women to spend their salaries on dressing like Sienna Miller on her way to a post-yoga beach party, lives in an apartment that is, satisfyingly, exactly how I'd imagined it. This is the Matthew Williamson aesthetic come to life: bright colours, dressed-up, an unjaded appreciation of pretty stuff and a hazy, cheerfully glamorised version of laid-back hippy chic. I buzz, and the door opens. "Hiya," Williamson says, his accent and choice of greeting still unmistakably Mancunian, 24 years after he left his home town for Central Saint Martins. "Come in, sit down, would you like a cup of tea?"

It is 15 years since Williamson burst on to the scene with Electric Angels, a catwalk debut that took him as close to overnight success as the relatively small-fry world of British fashion gets. It was 1997, and out of the dying embers of grunge and minimalism came Williamson's visual explosion of Indian pinks and Ibizan attitude. Fifteen years later – and in triumphant defiance of the odds on longevity for 25-year-olds who find instant fame and start hanging out with supermodels – Williamson is still a bold-faced name on the London fashion week schedule, with a team of 47 and flagship stores in London, New York and Dubai.

He is celebrating his anniversary with a short film starring Sienna Miller, eight Royal Ballet ballerinas and a corps de ballet of models and It girls. The film, made in a 19-hour day of filming at the grand Cotswold house of Aynhoe Park, tells the story of the past 15 years from the point of view of a 15-year-old Matthew, dreaming his career. It ends with his mum, played by Andrea Riseborough, standing at the bottom of a staircase and "shouting me down for my dinner, and a boy who looks like a 15-year-old me who's fallen asleep on the bed, reading Vogue".

As a child, Williamson was confused when his sister said she wasn't sure if she wanted to be a nurse or a teacher. "How could you not know? It was always so obvious to me. There was never any question. As soon as I knew what a fashion designer was, I knew that's what I was going to do." He says that this "came from my relationship with my mother, who I just absolutely adore – always have. In what was quite a grey, industrial, middle-class environment, I watched how she used fashion to make herself feel better, to brighten things. And I suppose seeing how fashion did that for her, in some subliminal way I wanted to make beautiful clothes as a way of enriching her life."

His father, who had named him after Sir Matt Busby, would buy him Christmas gifts of football boots; he never wore them. "I knew I couldn't be that archetypal northern male teenager, which was difficult. That was partly why I was so determined to get down to Saint Martins." During Williamson's student years, his dad accepted "that my being different wasn't something that had to be suppressed, or shunned. He's brilliant, my dad."

Around his neck, Williamson wears a gold pendant he was given on his 40th birthday last year, which is engraved "MW, love forever, Mum & Dad". Neither of his parents has missed a single catwalk show during his 15-year career. "Nor an after-party," he adds, raising an eyebrow. He is very funny, in the Mancunian way: more dry asides than punchlines. Listening to the tape after the interview, he keeps making me laugh, but there are no actual jokes to transcribe. That was why his friends urged him to make a film with humour: "I didn't want it to just be whimsical footage of girls wafting around in gorgeous dresses, because that's been done to death."

Saint Martins didn't quite turn out to be the haven the teenage Williamson was expecting. "I was 17, the youngest on a course of 60, and I was a bit too young for it. It was very unstructured, and I was a fish out of water, with everyone else doing conceptual fashion and me looking at photos of Rio carnival."

In fashion folklore, Williamson leapt straight from Saint Martins to the Electric Angels catwalk show of September 1997, when the industry packed into a tiny studio to watch models including Kate Moss, Jade Jagger and Helena Christensen parade the 11 outfits that would make Williamson's name. But the real sliding-doors moment of his career came before, the night he met Joseph Velosa, his one-time lover and lifelong best friend and business partner. Home for the weekend from college, Williamson was in a Manchester bar: "And this is the Stone Roses, Happy Mondays days, so everyone's in cagoules, and this guy walked in – very handsome, crisp shirt, white teeth..." They fell in love and Velosa, who was studying for a philosophy degree, transferred from Manchester to King's College London to be with him. After Saint Martins, Williamson took a job at Monsoon, where the trips to India crystallised his aesthetic and his determination to have his own label. He handed in his notice, and he and Velosa headed to India. After buying standby tickets, they had £90 in their backpacks. In India, they had some sample garments made, and "when we got back to London it was Joseph who was pushing me, saying, 'You need to show those to Vogue.' Like any couple in love, we were proud of what the other did."

So Williamson picked up Vogue, and looked down the masthead. "I had no idea how I should do this. I saw the name [fashion editor] Plum Sykes and I thought that was such a nice name, so I sent her a postcard." Sykes called him up, he took in his clothes and they made their way into the pages of Vogue, and on to a shoot for Tatler, the day after which Jade Jagger called up asking if she could keep the skirt. Velosa, who answered the phone, told her no, but said she could buy it. ("I was like, 'Give me the bloody phone – she can have the skirt!'") Williamson and Jagger met up, hit it off, and when he mentioned doing a show, she offered to ask her friend Kate Moss to model with her. "Kate came round and we sat on my bedsit floor and ate a McDonald's, and she pointed to the pink and turquoise dress and said, 'I'll do the show if I can wear that.' She saw something in the clothes. She's always had her eye on the next thing."

The model cast elevated industry reaction to the show, turning buzz into hype, but a misconception that annoys him is that having supermodel chums was how he got famous. "Those girls weren't my mates at that point, at all. They just did the show because they liked the clothes." The importance of Jagger and, later, of his model-muse Sienna Miller is nothing by comparison with that of Velosa, he says. The pair split as a couple after 12 years, but "we still have a brilliant relationship. I definitely wouldn't be where I am without him. He's probably more important in our success than me. And anyway, he's my best friend. I want to know him for ever." If he could save one possession from a fire, he says, it would be the watch he wears, a present from Velosa.

The same quality that has brought Williamson success – a crystal-clear identity that centres around Ibiza, India, colour, jetset and glamour – has also brought him angst. "At times it is suffocating and frustrating. People have such preconceptions of what we're about that even when there's nothing Indian or ethnic in the collection, they still put the same things in the reviews. I'm not putting out on the runway things that are changing the shape of fashion. I know that, and I'm cool with that. But there's still an enormous amount of skill involved. I like to look on the brighter side of things, but that doesn't mean there's no thought process. It's like a butterfly wing: the beauty may look flighty and natural, but it's incredibly precise and ordered."

There is solace to be found in the fact that, although there will be long periods when sexy party dresses are cold-shouldered by the grandes dames of fashion, the customer still wants them. For his collection at this month's London fashion week, "I thought, sod it, people bang on about India whatever I do, so instead of fighting it, I'm going to do India." Critics liked it almost as much as the buyers, who have never wavered.

The dream to become a famous fashion designer having come true, Williamson is in uncharted territory – "This is as far as my plan went. So, now what?" He describes his life as "at a nice level of fame. Fashion's quite niche, so it's all on a very manageable level. If I'm queueing in Starbucks, someone might come and say hello and ask for a picture. I love it when that happens. How brilliant, that someone wants a picture of me?"

Together with Velosa, he owns 52% of his business. In the next two months, the pair will visit Lagos, Shanghai, Qatar, Hong Kong, Dubai and Rome on business. Williamson is "on a break" from his latest beau, the model Stephen Baccari, "so I'm a one man and his dog, at the moment," he says.

We both turn to admire his glossy American cocker spaniel, who has been lounging on an Aztec throw in a corner of the sofa. I ask her name. "Coco," he says. As in Chanel? "Yes, which is tragic, I know. I'm such a cliché." He laughs, sounding perfectly content.